Objectives 



The major objective of this component of the SUPERTANK Laboratory 

 Data Collection Project was to measure instantaneous suspended sand 

 concentration and relevant fluid flow parameters at high cross-shore resolution 

 in the region of incipient and initial wave breaking. A secondary objective 

 was to measure, at high temporal and spatial resolution, the formation, 

 dispersal, and settling of the sand clouds created by plunging breakers. 



Scope 



To address the first objective stated above, a capacitance wave gauge, a 

 video camera, a vertical array of four electromagnetic current meters, and a 

 vertical array of five OBS were mounted to a carriage that spanned between 

 the walls of the wave channel (Figure 7-1). With this apparatus, time series 

 measurements of suspended sediment concentration, and other relevant param- 

 eters, were obtained in the region of transition from nonbreaking to fully 

 broken waves. The mobile array also enabled concentration measurements to 

 be obtained anywhere along the channel, to fill in between the fixed arrays. 

 In a few cases, high spatial resolution across shore was attained by moving the 

 carriage in a stepwise manner along the channel during a test. Initial analysis 

 of the concentration data shows significant change in sand suspension across 

 the zone of initial breaking, both in the behavior of the time series as well as 

 in the vertical distribution of mean concentration. 



Figure 7-1 . Movable carriage for measurements in breaking waves 



Chapter 7 Sediment Suspension Measurements from a Platform 



123 



